Softening water



Oct. 30, 1934.-

G. HEDRICHI 1,978,629

SOFTENING WATER Filed Aug. 29, 1952 if /8 f;

M fzyz wws zm Patented Oct. 30, 1934 UNITED STATES PATENT OFFICE 1,978,629 SOFTENIING warns.

Guido Hedrich, Budenheim, Germany, assignor to Chemlsche Fabrik Budenheim Aktlengesellschaft, Mainz, Germany Application August 29, 1932, Serial No. 630,920 In Germany September 3, 1931 4 Claims. (Cl. 210-16) This invention relates to a process and appato arrange the pipes in the manner best adaptratus for the softening of water and more pared to the space available, for example on locoticularly concerns a process and apparatus for motives or ships. Thus the requisite pipe lengths the softening of boiler-feed water. may be disposed in the available space entirely The usual apparatus for softening water, paror partially in the form of a bundle of pipes or 60 ticularly boiler-feed water, have the disadvanuse may be made of floors, walls and covers. The tage that, owing to the slow rate at which the. mixing action during the process of softening reaction between the hardening constituents of may be considerably increasedcby introducing the water and the reagents employed for precipiconstrictions, which may be capable of regulatating the same, proceed to completion, the voltion, at suitable points in the system. 6 nine of water under treatment is always a mul- The invention is not limited to any one definite tiple of that which is hourly required for use, for softening process; it is applicable with the like example for feeding steam boilers. As a conseeffect as regards increase of the rate of reaction, quence thereof the dimensions of the softening to any softening process, in which the hardening and purifying apparatus assume extraordinarily constituents of the water are rendered harmless large proportions, thus necessitating a correby precipitation with the aid of suitable chemispondingly large covered-in floor space in the cals. It is, however, applicable with particular boiler house as well as solid foundations and paradvantage to the process of effecting preliminary ticularly strong construction of the apparatus softening with alkaline residual boiler water and themselves. It is absolutely impossible to emcompleting the softening with alkali-phosphate. 75 ploy apparatus of such large dimensions in all In the accompanying drawing, Figure 1 is a moveable boiler plants, for exampleinlocomotives diagrammatic view, in elevation and partly in or ships, because the ballast would be unneces section, of the preferred embodiment of apparasarily increased thereby. Consequently such tus for carrying out the method; and Fig. 2 is a moveable boiler plants must either carry a small similar view, showing a modification of the ap- 8o supply of softened water for a short distance, paratus illustrated by Fig. l. which in turn necessitates the maintenance of a. In the modification shown in Fig. 1 the crude larger supply of softened water at definite stages water enters the top of the cascade preheater a, or recourse must be had to water which has not through the pipe 12 and is there preheated by been eillciently softened. steam entering at 0. Residual boiler water is in- The present invention provides a means for troduced through the pipe (I and becomes adeffecting the complete softening of water in the mixed with the water under treatment. Owing smallest possible space and consists therein that to the suitably selected difference in height bethe large reaction containers, usually employed tween the cascade preheater a and the reaction in softening processes involving the use of prepipes f the water flows through the pipes 3 to the 90 cipitating agents, are replaced by a system of filter i. 0n the way the alkalies present in the coils'of pipes, in which the interaction between residual boiler water react with the crude water the hardening constituents of the water and the and pre-soften the latter. The subsequent sofprecipitating chemicals, owing to the constant tening of the water may, for example, be effected 40 whirling motion of the water not only against by means of an alkali phosphate solution conthe walls of the pipes but also through the curves tained in the storage tank g and introduced of the same, proceeds to completion in the shortthrough the funnel h, which is disposed at a suitest imaginable time. The reaction period may able high position. The complete subsequent be still further very considerably shortened by softening of the water to 0 hardness takes place subjecting the whole system to elevated pressure in the pipe line between the funnel h and the filso that the temperature can be raised above the ter 2'. After the flocculent precipitate thrown normal boiling point of the water. down during the softening process has been sep- A filter of any desired suitable construction arated by t e fi te e Water passes o ac01- is inserted in the system of reaction pipes before lecting bOX from which the feed P p I feeds their entry into the steam boiler in order to eft s d Water into the Steam boiler Iect separation of the precipitated hardening con- In the modification shown in Fig. 2 the whole stituents. system stands under an excess pressure corre- It is not necessary that the pipes of the softensponding to the pressure in the boiler, thus heing plant should be bent or curved according to cessitating the whole plant taking the form of a any definite scheme. It is consequently possible closed system. The crude water is forced under no pressure by means of the feed pump 0 out of the storage container 11. into the pipe system 20. At the same time the pump q conveys residual boiler water Tfrom the steam boiler 3 through the pipe lead 1', as well as, if required, steam from the dome of the boiler through the pipe lead 13, by

way of the mixing nozzle it into the crude water.

In the first half of the passage through the system of reaction pipes pre-softening takes place owing to the interaction of the hardening constituents of the crude Water with the alkalinereacting residual boiler water. The residual hardness is removed, for example by compressing alkali phosphate solution by means of pump 10 from the storage tank 1) through the lead a: to a suitable point in the pipe system 17. After the subsequent softening process is completed in the latter half of the passage through the pipe system, the flocculent precipitate is separated from the water in the pressure filter y and the softened water introduced into the steam boiler. In the whole aggregate the pump 0 replaces the feed pump otherwise usually employed.

The following example serves to illustrate a process for softening water in the plant shown in Fig. 1.

The length of the pipe 1 from the cascade preheater a. up to the point at which the subsequent softening agent is introduced amounts to 15.3 metres and the interior cross section of the same to 21.6 square centimetres. 3050 litres per hour of crude water of 15 British total hardness are introduced through pipe b and 1350 litres per hour of alkaline residual boiler water through pipe d and the mixed waters conveyed onwards through the pipe 1. When the point It is reached the water is found to have a residual hardness amounting to 1.75 British hardness, which are precipitated with the aid of trisodium phosphate solution introduced from the container g. Complete softening to 0 hardness is effected in the line of pipe between h and the filter 1', having a total length of 10.5 metres, without any detectable excess of precipitating agent being present in the completely softened water. The total pipe line from a to 2', having a total length of 25.8 metres contains only 55.8 litres but passes hourly 3050+1350=4400 litres of feed water. The rate of fiow is accordingly 5'70 mm. per second. The

softening effect, in view of this high rate of flow, is surprising, because even the most recent literature (e. g. Stumper, Speisewasser- 8: Speisewasserpfiege, Springer, Berlin, 1931) directs that the capacity of the reaction container must amount to at least double the hourly requirement of water and the rate of flow of the water through the purifier, even when softening in the warm, must be less than 1 mm. per second.

Ci claim 1. A method for softening boiler feed water consisting in adding successively alkaline reacting boiler water and alkali metal phosphate to the water under treatment while flowing rapidly through a closed and unheated pipe system, effecting precipitation of the hardening constituents while the water is flowing through said pipe system, and separating the precipitated hardening constituents from the water.

2. A method for softening boiler feed water consisting in adding successively alkaline reacting boiler water and alkali metal phosphate to the water under treatment while flowing rapidly through a closed and unheated pipe system, effecting precipitation of the hardening constituents while the water is flowing. through said pipe system, and separating the precipitated hardening constituents from the water by filtration.

3. A method for treating feed water to soften the same in a boiler system, consisting in mixing the crude water with residual water from the boiler in a preheater into which steam is introduced from the boiler, leading the mixture from the preheater through an elongated reaction coil, introducing a chemical reagent into the reaction coil to commingle with the mixture of crude and residual water to precipitate the hardening constituents contained in the mixture, leading the treated water from the coil through a filter to separate the precipitate from the water, and discharging the filtered water from the filter into the boiler to provide the residual water.

4. A method for treating feed water to soften the same in a boiler system, consisting in passing a mixture of crude water and residual water from the boiler through an elongated reaction coil, introducing a chemical reagent into an interme- .diate part of the reaction coil to commingle with the mixture of crude and boiler water to precipitate the hardening constituents contained in the mixture, leading the treated water from the coil through a filter to separate the precipitate from the water, and discharging the filtered water from the filter into the boiler to provide the residual water.

GUIDO MDRICH. 

